Magnesium base alloy



Patented Mar. 22, 1932 UNITED STATES PATENT OFFICE ROBERT T. WOOD, 01' LAKEWOOD, OHIO, ASSIGNOR 'I'O AMERICAN MAGNESIUM CORPORA- 'IION, OI TITTSBURGH, PENNSYLVANIA, A CORPORATION OF NEW YORK MAGNESIUM BASE ALLOY No Drawing.

This invention relates to magnesium base alloys and is directed to the development of alloys of this class which will lend themselves readily to mechanical hot-deforming processes.

One of the major diflicuties heretofore encountered in adapting magnesium base alloys to commercial application has been that a wrought structure is particularly diflicult to attain in these alloys because of premature cracking or fracturing of the articles during working. Working of the alloys is desirable particularly in certain applications, as 1t 1s universally recognized that the refinement of grain and improvement in internal structure produced in the alloy by the working processes are attended by more favorable physical properties than can be e ualed in the case of castings. Heretofore it as been diflicult to mechanically deform magnesium base alloys even into simple shapes, and wrought articles of intricate design were in some cases practically impossible to produce in these alloys, although the same articles could be commercially manufactured in the wrought condition from alloys other than those containing a preponderance of magnesium.

The principal object of the invention is the provision of magnesium alloys which can be successfully worked into articles of more intricate design than were heretofore commercially producible.

A further object of the invention is the provision of magnesium alloys which are more plastic over a wider range of working temperatures than the magnesium alloys heretofore available.

A further object of the invention is the provision of magnesium working alloys characterized by high corrosion resistance. A further object is the provision of magnesium working alloys with desirable mechanical properties.

The terms ma esium alloy and magnes1um base allo as used herein and in the Serial No. 562,599.

appended claims denote an alloy containing more than er cent of magnesium.

In a copencling application of Harold H. Block and myself, Serial No. 555,532, filed August 6, 1931, magnesium base alloys are described and claimed containing tin, zinc, and cadmium, with or without manganese, lead or mercury. These alloys throughout the claimed limits are improved casting alloys of high corrosion resistance, but in some cases they are amenable to the ordinary working processes under certain conditions.

I have discovered that magnesium base alloys containing from 0.1 per cent to 15.0 per cent tin and from 0.1 per cent to 5.0 per cent manganese, with or without certain other constituents described more in detail hereinafter, are more adaptable to mechanical deformation than the magnesium base working alloys at present available. Over the whole composition range outlined the alloys may be extruded, but if they are intended for rolling or forging it is best to employ a tin content of about 5.0 per cent to 7.0 per cent, in which case the manganese content may be between about 0.5 and 1.5 per cent. For optimum working qualities an alloy with about 6.0 per cent tin and 1.0 per cent manganese is preferred. This alloy in the extruded condition and. without additional treatment has a tensile strength of about 42,600 pounds per square inch and an elongation of about 13.0 per cent in 2 inches. These properties, while very favorable, are not unusual and prior to this invention equally good tensile strength and elongation have been obtained from commercial magnesium base wrought alloys. The advantages of the present invention are found in the ease with which the alloy can be deformed, the high corrosion resistance of the product, and the latitude permissible in the choice of a working temperature.

In general I prefer to use a manganese content not much, if any, below about 0.5 per cent, but advantageous results have been obtained with lower amounts.

The magnesium base allo of the prior art most widel used in the nited States as a working al oy requires considerable care and attention to detail to obtain wrought products therefrom, and can be worked only between about 500 F. and 800 F., a working range of 300 F. At about 820 F. or over the alloy is hot short and is extremely liable to fracture under the application of the working force, and at temperatures lower than about 500 F. too much mechanical energy is required to deform the billet.

My preferred alloy containing about 6.0

per cent tin and 1.0 per cent manganese can be hot worked successfully between 950 F. and about 450 F., a working range of 500 F. The higher working temperatures, as well as the nature and amount of the alloying constituents, cooperate to produce an internal structure which is characterized by a considerably improved plasticity. I have been able to produce from this alloy wrought articles of such intricate design that all attempts to form them from the magnesium base alloys heretofore available resulted in failure even under the most careful working conditions.

This alloy and other combinations comprised herein have been subjected to severe tests under particularly aggravated corrosive conditions. One such test which has been standardized for the purpose of comparing different alloys consists in repeated immersions of the test specimen in a 3 per cent aqueous solution of sodium chloride alternating with exposures to the atmosphere. This test was chosen principallv for the reason that its severity is productive of numerically measurable corrosion effects within a fairly short time and a duration of 40 hours has been adopted as a standard.

In carrying out the test a number of tensile specimens identical as to composition and fabricating conditions are divided into two groups and one group is tested for physical properties, for instance, tensile strength. The other group is put through the alternate immersion test described and is tested at the con clusion of the procedure. The difference between the average strengths of the two groups is a measure of the deterioration from corros1on.

The commercial magnesium base working alloy mentioned above at the end of 40 hours of test lost 61 per cent of its original strength. Although there was an a pearance of surface corrosion evident to t e eye, the tensile stren h of my preferred alloy was unim paire indicating that the alloy is characterized by very hi h resistance to corrosion. Such an improved resistance displayed b the preferred composition quoted can hard y be attained over the whole composition range claimed herein, but very substantial improve- Tensile 3:32:! Per cent strength zg gl Brinell um tin lg, n. on hardness 1 2 41, 630 5. 0 50. 7 l 4 42, 790 12. B 51. 4 l 6 42, 690 13. 7 55. 3 1 10 42. 350 5. B B0. 8

Samples of these alloys, after being subjected to the corrosion test, uniformly displayed no appreciable corrosive effect.

While the magnesium base alloys containing tin and manganese are entirely satisfactory for the pur oses above described, it may be found desira le that the strength of these alloys be increased without decreasing, to any large extent, their favorable working properties and corrosion resistance. For the purpose of obtaining such strength increase, I have discovered that certain alloying elements, namely zinc, lead, calcium, cadmium and/or barium, ma be added to the alloys without deleterious y affecting the working or corrosion-resistance qualities of the same. While these alloying elements may be added to the magnesium base alloys containing tin and manganese for effecting a general purpose, their effect is not strictly equivalent in view of the fact that the effective amounts of elements which may be added to the alloy vary and in some cases one element produces efi'ects in the alloy not obtained by another. In the addition of the above named alloying elements for the general purpose of hardening the alloys, a compromise may be reached between the advantages produced by this addition and the disadvantages of increasing the specific gravity of the alloy as the percentages of the heavier elements contained therein are increased. In no case should the magnesium be less than 50 per cent of the alloy by weight.

Zinc may be added to the magnesium base alloys containing tin and manganese in amounts of about 0.1 per cent to 10 per cent and when added in such amounts the zinc increases the strength of the alloys. When the alloy is to be used for forging and similar working processes, additions of less than 1 per cent of zinc are preferred. But if the alloy is to be extruded, zinc may be added in amounts as high as 10 per cent. The addition of zinc to these alloys increases somewhat their susceptibility to heat treatment.

Lead may be added to the magnesium base alloy containing tin and manganese in amounts from 0.5 to about 5 per cent and when so added, materially increases the strength of the alloy without appreciably decreasing its working characteristlcs or its susceptibility to corrosion. Because of the weight of this alloying element, I do not prefer to add it in amounts much greater than about 5 per cent by weight.

Calcium may be added to the magnesium base alloy containing tin and manganese for the purpose of strengthening the alloy and this purpose is most satisfactorily achieved if the metal is present in amounts of about 0.1 per cent to 2 per cent. The addition of much more than about 2 per cent of calcium to these alloys, while increasing their hardness, tends to make the alloy brittle. Barium may be substituted in the magnesium base alloys con taining tin and manganese for calcium, or both calcium and barium may be added together. The amount of either calcium and/or barium should preferably be not more than about 2 er cent. Another alloying element which I have found desirable in its tendency to strengthen the magnesium base alloy containing tin and manganese is cadmium. This alloying element I prefer to add in amounts of about 0.5 per cent to 10 per cent. The hardness imparted to the alloy by the cadmium in amounts under about 5 per cent is not great and for this reason I preferably add amounts of about 5 to 10 per cent of cadmium, although less amounts of cadmium may be used, particularly Where it is nfit the only hardening element added to the a 0y.

The above mentioned alloying elements, zinc, lead, calcium, cadmium, and barium, may be used separately in the magnesium base alloy containing manganese and tin or two or more of these elements may be used for the purpose of achieving like results.

The alloy is preferably compounded by adding a tin manganese-rich alloy to molten magnesium. The tin manganese-rich alloy is made by adding metallic manganese to molten tin and heating the melt preferably to more than 1000 F. beyond which point appreciable solution of manganese in tin takes place. After solidification and chemical analysis the proper proportions of rich alloy and magnesium can easily be calculated. The method of making up the tin -manganese alloy herein disclosed is claimed in my copending application Serial No. 504,429, filed December 23, 1930.

The alloys herein disclosed and claimed may be subjected to theusual thermal treatments for the purpose of improvingor altering certain of the properties and in the claims appended hereto the term magnesium alloy or magnesium base alloy denotes the alloy either'in the heat-treated or the unheat-treated condition.

This application is a continuation in part of my earlier application Serial No. 504,428, filed December 23, 1930.

What I claim is- 1. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin and 0.5 per cent to 5.0 er cent manganese.

2. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, and 0.1 per cent to 5.0 per cent lead.

A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, and 0.1 per cent to 10.0 per cent cadmium.

4. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, and 0.1 per cent to 2.0 per cent calcium.

5. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 5.0 per cent lead, and 0.1 per cent to 10.0 per cent cadmium.

6. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 5.0 per cent lead, and 0.1 per cent to 2.0 per cent calcium.

7. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 10.0 per cent cadmium, and 0.1 per cent to 2.0 per cent calcium.

8. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 10.0 per cent cadmium, and 0.1 per cent to 2.0 per cent barium.

9. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.01 per cent to 1.0 per cent calcium, and 0.1 per cent to 1.0 per cent barium.

10. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 5.0 per cent lead, 0.1 per cent to 10.0 per cent cadmium, and 0.1 per cent to 2.0 per cent calcium.

11. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 5.0 per cent lead, 0.1 per cent to 10.0 per cent cadmium, and 0.1 per cent to 2.0 per cent barium.

12. A magnesium base alloy containing 0.1 per cent to 15.0 per cent -tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 5.0 per cent lead, 0.1 per cent to 1.0 per cent calcium, 0.1 per cent to 1.0 per cent barium.

13. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 10.0 per cent cadmium, 0.1 per cent to 1.0 per cent calcium, and 0.1 per cent to 1.0 per cent barium.

14. A magnesium base alloy containing 0.1

per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 5.0 per cent lead, 0.1 per cent to 10.0 per cent cadmium, 0.1 per cent to 1.0 per cent calcium, and 0.1 per cent to 1.0 per cent barium.

15. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, and 0.1 per cent to 2.0 per cent barium.

16. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin and 0.1 per cent to 5.0 per cent manganese.

In testimony whereof I hereto aflix my signature.

ROBERT T. WOOD.

DISCLAIM ER 1,85Q,613.Robert T. Wood,'Lakewood, Ohio. MAGNESIUM Base ALLOY. Patent L dated March 22, 1932. Disclaimer filed May 29, 1934, by theassignee,

Magnesium Development Corporation, with the Aluminum Company of Amerwu, assenting and joining. Enters this disclaimer to ceitain of the claims of the above-identified patent,

namely, claims 1 and 16. [Qfl ial Gazette June 19, 1934.]

per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, 0.1 per cent to 5.0 per cent lead, 0.1 per cent to 10.0 per cent cadmium, 0.1 per cent to 1.0 per cent calcium, and 0.1 per cent to 1.0 per cent barium.

15. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent manganese, and 0.1 per cent to 2.0 per cent barium.

16. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin and 0.1 per cent to 5.0 per cent manganese.

In testimony whereof I hereto aflix my signature.

ROBERT T. WOOD.

DISCLAIM ER 1,85Q,613.Robert T. Wood,'Lakewood, Ohio. MAGNESIUM Base ALLOY. Patent L dated March 22, 1932. Disclaimer filed May 29, 1934, by theassignee,

Magnesium Development Corporation, with the Aluminum Company of Amerwu, assenting and joining. Enters this disclaimer to ceitain of the claims of the above-identified patent,

namely, claims 1 and 16. [Qfl ial Gazette June 19, 1934.] 

